The primary goal of this project is to characterize Lyme encepahlopathy. The case group includes patients with late untreated disseminated infection and chronic Lyme patients with post treatment syndromes 3 or more months following completion of antibiotic treatment (n=100). The first control group will consist of 100 population based healthy individuals who will be compared to case group regarding neurobehavioral measures. The second control group will consist of the CSF specimens from 50 other Neurologic Disease (OND) Controls which will be served as a quality control for the CSF measures performed on the case groups. By defining the clinical features and pathophysiology of Bb associated encephalopathy, rational treatment strategies can be designed. This project involves an 18 month longitudinal evaluation of late untreated disseminated Bb infection and post Lyme syndrome (n=100). The Specific Aims are: 1. To define the neurobehavioral and psychological sequelae of chronic Lyme disease. 2. To determine the pathogenesis for neurobehavioral deficits in chronic Lyme disease. 3. To identify the clinical and laboratory factors which predict health outcome in chronic Lyme disease.